In form, a word is simply any uninterrupted sequence of alphanumeric characters (which include - amongst a few other oddities - periods and commas). In this light, slow.down is a word (one word) and 10 is a word just as much as fido is. (How 10 is actually understood in LOGO depends in part on the fact that we write it with digits, but it also depends on how we choose to operate on it. If you try to add together 10 and 5, LOGO well certainly tell you that the result is 15 - because 10 and 5 are instances of a special sub-class of words called numbers - but at the same time you can request the first 'letter' of the word 10, and you will find yourself given quite naturally the character 1.)
A list, like a word, is also a sequence, but the constituents of a list may be either, in the simplest case, words - e.g. [lion tiger hyena] - or, in more complex cases, other lists - e.g. [ [jan stewart] [dan'l widdon] [old uncle tom cobbley] ]. Sometimes, if need be, they may be a mix of the two - e.g. [[dan'l widdon][eyes [bright blue][hair [dark brown]]. In LOGO, a list is identified by opening and closing square brackets.
In the limit a word may contain no characters and a list may contain no elements. The empty list - and there is of course only one empty list - is represented by opening and closing square brackets with nothing (or only the separator character, a space) between. The empty word is represented as a double quote mark followed by nothing. (A space after " separates it from the next word.)
Collectively, words and list structures are known as Logo objects
At first glance, it is not unreasonable to feel that although a Logo word may mean what you like, the the stark simplicity of the available data types - just words and lists - is bound impose serious limitations on Logo's ability to handle complex pheneomena. In practice, however, you will find it difficult to discover restrictions on the ideas which can be expressed. On reflection, this is not really too surprising. The basic LOGO objects, word and list, are directly analogous to the words and sentences of natural language. And presumably you are prepared to accept the proposition that in any natural human language we can talk about whatever we like.
[beaune k6 [[dijon 45] [chalon.sur.saone 30] [pouilly.en.auxois 46] [seurre 26]]]
[[cloth wool] [sleeves raglan] [belt buckled] [buttons [3 [black]]]. . .]
[[milk.shake coffee root.beer] chips [big.mac cheeseburger] [apple.pie ice.cream]]
[[diaz 1486 1487 S.Africa] [columbus 1492 1498 C.America] [cabot 1497 1498 N.America] [da.gama 1497 1498 India] [magellan 1521 1522 all.the.way.round]]
[BA 747 [london rio] [[smith evans . . .][jones sims webb . . .]]]
[[3 20] [11 28] [16 35] [22 37] [26 10] [39 5] [49 67] . . .]
Lists in LOGO - take the overcoat as an example - can contain lists which themselves contain lists which themselves . . . And the nesting can in principle be continued ad infinitum, even if in practice the memory of your system will at some point force a halt.